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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2017-428
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2017-428
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 19 Oct 2017

Submitted as: research article | 19 Oct 2017

Review status
This discussion paper is a preprint. A revision of this manuscript was accepted for the journal Biogeosciences (BG) and is expected to appear here in due course.

Changes in gross oxygen production, net oxygen production, and air-water gas exchange during seasonal ice melt in the Bras d'Or Lake, a Canadian estuary

Cara C. Manning1,2,3,a, Rachel H. R. Stanley4, David P. Nicholson2, Brice Loose5, Ann Lovely5, Peter Schlosser6,7,8, and Bruce G. Hatcher9 Cara C. Manning et al.
  • 1MIT/WHOI Joint Program in Oceanography/Applied Ocean Science and Engineering, Woods Hole, MA, USA
  • 2Department of Marine Chemistry and Geochemistry, Woods Hole Oceanographic Institution, Woods Hole, MA, USA
  • 3Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA, USA
  • 4Department of Chemistry, Wellesley College, Wellesley, MA, USA
  • 5Graduate School of Oceanography, University of Rhode Island, Naragansett, RI, USA
  • 6Lamont-Doherty Earth Observatory of Columbia University, Palisades, NY, USA
  • 7Department of Earth and Environmental Sciences, Columbia University, Palisades, NY, USA
  • 8Department of Earth and Environmental Engineering, Columbia University, New York, NY, USA
  • 9Department of Biology and Bras d'Or Institute, Cape Breton University, Sydney, NS, Canada
  • anow at: Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC, Canada

Abstract. Sea ice is an important control on gas exchange and primary production in polar regions. We measured net oxygen production and gross oxygen production using near-continuous measurements of the O2 / Ar gas ratio and discrete measurements of the triple isotopic composition of O2 in the Bras d'Or Lake, an estuary in Nova Scotia, Canada, as the bay transitioned from ice-covered to ice-free conditions. The volumetric gross oxygen production was 5.4(+2.8−1.6) mmol O2 m−3 d−1, similar at the beginning and end of the time-series, and likely peaked at the end of the ice melt period. Net oxygen production displayed more temporal variability and the system was on average net autotrophic during ice melt and net heterotrophic following the ice melt. We performed the first field-based dual tracer release experiment in ice-covered water to quantify air-water gas exchange. The gas transfer velocity at > 90 % ice cover was 6 % of the rate for nearly ice-free conditions. Published studies have shown a wide range of results for gas transfer velocity in the presence of ice, and this study indicates that gas transfer through ice is much slower than the rate of gas transfer through open water. The results also indicate that both primary producers and heterotrophs are active in Whycocomagh Bay during spring while it is covered in ice.

Cara C. Manning et al.
Interactive discussion
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AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Interactive discussion
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
Cara C. Manning et al.
Data sets

Oxygen/argon, triple oxygen isotope, and CTD data from Bras d'Or Lake, Nova Scotia, Canada, version 2 C. C. Manning and R. H. R. Stanley https://doi.org/10.5281/zenodo.1011216

Model code and software

calcGOP: MATLAB functions for the calculation of gross oxygen production from triple oxygen isotope data used in Manning et al. (2017) Geophysical Research Letters, release 1.0 C. C. Manning and E. M. Howard https://doi.org/10.5281/zenodo.376786

Cara C. Manning et al.
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We measured rates of biological activity and gas exchange in a Canadian estuary during ice melt. We quantified gas exchange using inert, deliberately-released tracers and found that the gas transfer rate at > 90 % ice cover was 6 % of the rate for nearly ice-free conditions. We measured oxygen concentration and isotopic composition and used the data to detect changes in the rates of photosynthesis and respiration (autotrophy and heterotrophy) as the ice melted.
We measured rates of biological activity and gas exchange in a Canadian estuary during ice melt....
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